Many types of impoundments are currently in use for the storage and disposal of hazardous materials. Examples include landfills, surface tanks, underground tanks, and various kinds of vault structures. A major concern regarding all impoundments containing hazardous material is the migration of the material away from the impoundment and into the environment where it can pose a significant danger to public health and safety.
To alleviate the risk of environmental contamination, government regulations require the installation (in many situations) of one or more impermeable synthetic liners, known as secondary containment systems, below landfills and many other impoundments of hazardous or potentially hazardous materials. The liners typically are large sheets of flexible, polymeric material, such as high density polyethylene, and are intended to resist degradation caused by the environment and contact with caustic hazardous waste. During construction of the impoundment, individual sheets of the liner material are seamed together at the construction site to form a continuous, impermeable liner which extends below and completely encompasses the bottom of the impoundment. Where more than one liner is used, a layer of clay or some other material having a low permeability is often placed between the liners.
Government regulations also require that the liners or secondary containment system be augmented by a number of monitoring wells at locations surrounding and adjacent to the impoundment. The purpose of the monitoring wells is to allow for the periodic testing of groundwater below the impoundment. The detection of hazardous material in the groundwater indicates a failure of the secondary containment system.
There are, however, some serious shortcomings associated with the use of synthetic liners and monitoring wells for the safe storage and disposal of hazardous waste. First, synthetic liners unfortunately have a tendency to develop leaks over time. The leaks can be caused by a number of factors such as punctures, split seams, and differential settling of the underlying soil. Once such a leak occurs, there is nothing to prevent the hazardous material from escaping the impoundment and contaminating nearby soil, surface water, and groundwater. Second, when a leak is first discovered through the detection of hazardous material in a groundwater sample taken from a monitoring well, significant damage to the environment will have already been inflicted. The hazardous waste will have already contaminated groundwater, an important source of public drinking water. Finally, the detection of hazardous waste in samples taken from the monitoring wells only reveals the existence of a leak, it provides little or no information as to the location and severity of the leak. Consequently, to correct the problem, it is necessary to remove the entire impoundment and completely replace all synthetic liners at an enormous financial cost. Such remedial measures also pose an increased danger to public health and safety because of the additional contact with the relocated hazardous waste.
Therefore, there is a need for a system which will provide early detection of a leak in an impoundment of hazardous or potentially hazardous waste materials, provide information as to the location and severity of the leak so that less extensive and less costly remedial measures may be taken, and which will safely contain the leak and prevent the escaping fluid from contaminating the environment.